[wip]: remove @types/jest everywhere

[mrazauskas]

Summary

This is an experiment to see how easy (or hard) it could be to remove @types/jest from jest repo. Motivation is simple: own types of the repo are good enough (in some cases even better) than the ones from @types/jest.

Todo:

• Figure out how to type Jest globals in test files (also the ones in examples directory).

Test plan

Green CI

[SimenB]

Exciting!!

I played with this for 15 minutes last night without being able to make TS augment the global env. Hopefully you can figure out the correct incantation 😀

[mrazauskas]

Found two possible solutions.

First was sort of workaround. It augmentation work. The whole idea was to emit a .d.ts file into node_modules/@types/jest directory as a final build step. This did not look elegant.

I though to try explicit imports. Why not? Went through all *.test.ts files and added import {expect, jest, ...} from '@jest/globals'; Exactly 300 files changed. That’s minimal change, so I hope review is doable if such migration is acceptable.

Unfortunately, few tests have jest.mock related error. That’s unexpected. Just pushed a single test file with that error. It shows up in CI as well. @SimenB does it look familiar? Hard to grasp what is going on (;

[mrazauskas]

Hm.. Just a transpiler issue? If globals are imported, Babel playground is transpiling the problematic line const realFs = jest.requireActual('fs'); into const realFs = _globals.jest.requireActual('fs'); This could be the explanation.

[mrazauskas]

Here is a minimal reproduction – https://github.com/mrazauskas/x-jest-globals. I simply added explicit import to this example – https://jestjs.io/docs/next/mock-functions#mocking-partials

Only wondering if this is a bug or expected behaviour?

[SimenB]

It's supposed to change the import, it's not supposed to tag it in the babel plugin. 😅 Can you open up a bug report with it so we can track it separately?

[mrazauskas]

Closing in favour of #12856

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